1. Field of the Invention
The present invention relates to a sensing technology of a touch sensor, and more particularly, to an apparatus for and method and medium of adaptively setting a reference sensing boundary of a touch sensor in which a reference sensing boundary of a touch sensor is set adaptively so that a value measured by the touch sensor is output only when the value is within the set reference sensing boundary.
2. Description of the Related Art
In general, touch type switches are becoming more commonly used than pushbutton type switches in consumer electronic products or liquid crystal display (LCD) monitors. In touch switches, an electrode is disposed inside a front surface cover of a product, and if the electrode part is touched by a user's finger, a change in capacitance induced between the electrode and the person is sensed, and this sensing signal is transferred as a switch signal to a microprocessor or a microcomputer.
In this touch switch method, when a person approaches an electrode disposed in a predetermined position, in order to sense a change in capacitance induced between the electrode and a person in contact with the electrode, or a change in inductance or impedance, a signal comparator is used sometimes. In a conventional signal comparison method, a sensed value is typically compared with a reference value, which is a preset value. Accordingly, two inputs are always required: an input for setting a reference value and an input for sensing a value.
In addition to the capacitance, in order to compare all analogue signals, the conventional technology requires adjustment for setting reference values according to various conditions and environments of an apparatus attached to a circuit that performs comparisons using a voltage comparator, a current comparator and a frequency comparator. Accordingly, in the development and mass-production of switches, cost and time increase. Even after a reference value is set, the conditions under which the reference value was set change with respect to changes in the surrounding conditions or changes in the environment, which causes difficulties in the maintenance and modification of the reference value.
Korean Patent Laid-Open Application No. 2005-0055156 discloses a technology used to solve the problem mentioned above. In this technology a sensing method and apparatus for a digital sensor use a method of automatically setting a reference value. According to the technology, the difference between a stored reference signal and a sensed signal is obtained for comparison, and if the sensed signal is greater than the reference signal for a predetermined time, the reference signal is updated with the sensed signal. That is, changes in capacitance caused by a human body and environmental changes are determined with respect to time.
However, according to the above technology, when a user's hand is wet or a touch sensor is used in a humid environment, the reference value changes and cannot be lowered until the system is completely reset. Accordingly, changes in capacitance due to actual contact with a human body cannot be sensed and the touch sensor is not suitable to be used for a portable device.